Li Jiancheng

Li Jiancheng (589-2 June 626) was Crown Prince of Tang China under his father, Emperor Gaozu of Tang. He was murdered by his younger brother, the future Emperor Taizong of Tang, in 626 during a bloody sibling rivalry.

Biography
Li Jiancheng was born in 589, the oldest son of the future Emperor Gaozu of Tang. His father showed preference to the middle child, the future Emperor Taizong of Tang, when selecting one of his sons to serve as a general, causing Li Jiancheng to resent Taizong, and causing factions to form at the Tang court during the 620s. In 626, Li Jiancheng advised their father to send the youngest brother, Li Yuanji, to fight the Gokturks instead of sending Taizong, a blatant insult to Taizong. Taizong responded by spreading rumors that Jiancheng and Yuanji had been committing adultery with their fathers' concubines, forcing the two brothers to return to Luoyang to answer to the charges. Before they could do so, they were ambushed at Xuanwu Gate by Taizong and his subordinates, and both of them were killed.